Extrusion process and product
a technology of extrusion process and product, which is applied in the direction of insulating conductor/cable, plastic/resin/waxes insulator, coating, etc., can solve the problems of affecting the ultimate use of the insulating conductor, consuming and economically infeasible, and not clear whether the ddr should be increased or decreased, so as to reduce the melt temperature and high quality
Active Publication Date: 2009-08-25
THE CHEMOURS CO FC LLC
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- Description
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- Application Information
AI Technical Summary
Benefits of technology
The present invention provides a process for forming insulation on a conductor that can achieve consistent high line speed operation and high quality insulation despite normal variation among manufacturers and equipment. The process involves extruding and melt drawing a melt-flowable fluoropolymer at a specified melt temperature and melt flow rate, cooling the resultant insulation, and winding up the resultant insulated conductor at a line speed of at least about 1750 ft / min. The process is preferably carried out using a fluoropolymer with a high melt flow rate and a low melt temperature. The resulting insulation is defect-free and meets the requirements for acceptable quality insulation. The process provides an operating window for the extrusion / melt draw-down process that is broad enough to accommodate small variations in the fluoropolymer's melt flow rate and still achieve high quality insulation at high line speed.
Problems solved by technology
The problem has arisen that when the fluoropolymer is supplied to a multiplicity of insulated conductor manufacturers, the extrusion / melt draw-down process is carried out under a variety of conditions, resulting in the fluoropolymer performing better for some manufacturers than for others, and for each manufacturer, better on some days than on others.
A spark failure indicates a fault in the insulation.
Lumps in the insulation interfere with the ultimate use of the insulated conductor; e.g. twisting together to form twisted pair conductors, pulling the insulated conductor through narrow openings.
This is time-consuming and economically infeasible and moreover, it is not clear whether the DDR should be increased or decreased in order to solve insulation quality problems at high line speed.
Success by temperature changes tends to be temporary, because some other change in the process or in the polymer adversely affects the quality of the insulation.
Faced with the onset of quality (spark and / or lump) problems, and at least the uncertainty of changing DDR, operating temperatures, and cone length, the manufacturer typically reduces line speed until the desired quality insulated conductor is reached, resulting in a loss of productivity.
From the standpoint of the fluoropolymer manufacturer, the challenge is whether there is improvement possible in the fluoropolymer that the would accommodate the unavoidable differences among customers and among extruders and their operators and permit high quality insulated conductor to be made at high speeds.
Method used
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Experimental program
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Embodiment Construction
[0026]To demonstrate the methodology of the present invention, the tetrafluoroethylene / hexafluoropropylene copolymer of Example 10 of U.S. Pat. No. 5,703,185 is selected. The copolymer contains a small amount of copolymerized PEVE. A series of extrusion / melt draw-down processes are conducted using the extruder for melt draw-down extrusion coating of the copper conductor, all as described in Example 10. The line speed is 2000 ft / min (610 m / min). The melt temperature of the copolymer is the temperature of the molten copolymer in the transition section between the extruder and the crosshead wherein the molten resin and the conductor are both traveling in the same direction. The melt temperature is measured by a thermocouple contacting the melt. This is the general procedure used in the tests described hereinafter. 45,000 ft (13.7 km) lengths of fluoropolymer insulated copper conductor are produced, which are then tested for sparks and lumps. The average of three runs (3×13.7 km lengths...
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Abstract
The present invention relates to the process of extruding melt drawing fluoropolymer onto conductor to form insulated conductor at a line speed of at least 533 m / min and having no more than 10 sparks and no more than 2 lumps / 13.7 km of insulated conductor under conditions that comprise an adequate process window to allow for these results to be obtained at different conditions within the process window. The invention identifies the critical parameters for achieving this process window, namely melt flow rate of the fluoropolymer, preferably being 30±3 g / 10 min, and the melt temperature of the extruding / melt-drawing step, preferably being 393° C.±6° C.
Description
BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]This invention relates to an improved process for coating a conductor with fluoropolymer insulation and to a fluoropolymer therefor.[0003]2. Description of Related Art[0004]U.S. Pat. No. 5,703,185 discloses an improved fluoropolymer, wherein the improvement enables the fluoropolymer to be extruded and the molten polymer to be drawn down (melt-draw down) to form insulation on a conductor at higher line speeds. Extrusion / melt draw-down to form insulated conductor is shown on pp. 17-19 of the TEFLON® / TEFZEL® Melt extrusion Guide, published by the DuPont Company in March, 1993. The extrusion conditions in Example 10 of '185 include the line speed, the draw down ratio for the melt draw-down step (97:1), the melt temperature increasing from 757 to 774° F. (403 to 412° C.) as the line speed is increased, and the copolymer having a melt viscosity (MV) of 2.37×103 Pa.s at standard conditions. This melt viscosity is calculated fr...
Claims
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IPC IPC(8): C08F16/24B29C48/06B29C48/154B29C48/92C08F14/26C08F14/28C08F214/26H01B3/44H01B13/14H01B19/00
CPCB29C47/025B29C47/92H01B3/445H01B19/00C08F214/26B29C47/0016B29K2027/12B29C48/92B29C2948/92209B29C2948/92704B29C2948/92876B29C48/06B29C48/154B29C2948/9238
InventorDEFEO, PATRICK ANTHONYHEFFNER, GLENN W.MCKEE, NIALL D.VENKATARAMAN, SUNDAR KILNAGAR
OwnerTHE CHEMOURS CO FC LLC